DE69602692T2 - Use of dye-plastic compositions that are resistant to chlorinated water and objects made from them - Google Patents

Abstract

A resin composition comprising a polyolefin resin, a pigment and a copolymer resin obtainable from a monomer having an alpha , beta -unsaturated double bond and a dibasic acid having an unsaturated double bond or an anhydride thereof is useful for preparing a molded article, such as a water-supply pipe. Dot-like projections and small-diameter blisters are not formed on the surface of the molded article when the surface is brought into contact with chlorine-containing water.

Description

The present invention relates to the use of a resin composition in connection with the transportation of chlorinated water. More specifically, it relates to the use of a resin composition which is resistant to chlorinated water and which can be used to produce a molded article which does not show point-like projections or bubbles of small diameter on its surface when in contact with chlorinated water.

To obtain colored molded articles from polyolefin resins, e.g. from polyethylene, polypropylene, etc., the polyolefin resins are colored by using an inorganic pigment such as zinc oxide, titanium oxide, red iron oxide, ultramarine or cobalt blue, an organic pigment such as an azo, quinacridone, anthraquinone, perylene, isoindolinone, phthalocyanine, dioxazine, indanthrene, perinone or quinophthalone pigment, or a dye such as an azo, anthraquinone, perylene, perinone or thioindigo dye.

When a molded article made of a polyolefin resin containing the above-mentioned pigment or dye is used in a portion where the molded article comes into direct contact with chlorinated water, such as a water supply pipe, a problem arises that small-diameter point-like projections or bubbles (hereinafter referred to as "bubbles") are formed on the surface of the molded article and then peel off, partially entering the water.

Water supply pipes in particular are subject to strict design standards to prevent the occurrence of bubbles, as laid down in JIS K6762, since the water is used for cooking and drinking water.

Therefore, a two-layer pipe has been proposed, the inner layer of which in direct contact with chlorinated water contains no pigment and the outer layer of which contains pigment. However, compared with single-layer pipes, the aforementioned double-layer pipe is difficult to manufacture and requires a special molding press. In addition, the manufacture of a double-layer joint between one pipe and the next is difficult. Therefore, the development of a colorant (colored) resin composition capable of providing a molded article with excellent resistance to chlorinated water is desired.

An object of the present invention is to provide a colorant (colored) resin composition which can be used for transporting chlorinated water.

According to the present invention there is provided the use of a resin composition comprising:

(a) a polyolefin resin;

(b) a pigment; and

(c) a copolymer resin preparable from a monomer having an α,β-unsaturated double bond and a dibasic acid having an unsaturated double bond or an anhydride thereof,

when transporting chlorinated water.

Typically, the resin composition contains 100 parts by weight of the polyolefin resin, 0.01 to 10 parts by weight of the pigment and 0.005 to 10 parts by weight of the copolymer resin.

The resin composition may also contain 100 parts by weight of the polyolefin resin; 0.1 to 100 parts by weight of the pigment and 0.05 to 100 parts by weight of the copolymer resin.

According to the present invention, there is also provided a water supply pipe made of the above-mentioned colored resin composition. Typically, the water supply pipe is a drinking water pipe.

The polyolefin resin used in the present invention includes polyethylene, polypropylene and polybutene. Of these, polyethylene and polybutene are preferred. The polyethylene includes various kinds of polyethylene such as a high density polyethylene (H), a low density polyethylene (L) and a linear low density polyethylene (LL). Generally, a high density polyethylene (H) is used for producing a water supply pipe with a large diameter, and a linear low density polyethylene is used for producing a water supply pipe with a small diameter.

The pigment used in the present invention includes inorganic pigments such as zinc oxide, titanium oxide, red iron oxide, ultramarine or cobalt blue, and organic pigments such as azo, quinacridone, anthraquinone, perylene, isoindolinone, phthalocyanine, dioxazine, indanthrene, perinone or quinophthalone pigment. Generally, water supply pipes are colored blue to resemble water, as opposed to green colored gas supply pipes or others. Therefore, the pigment is typically a blue pigment. Suitable blue pigments include ultramarine, cobalt blue, a phthalocyanine blue pigment and an indanthrene blue pigment. Preferably, the blue pigment is a phthalocyanine blue pigment and/or an indanthrene blue pigment. Typically, the phthalocyanine blue pigment is a copper phthalocyanine blue pigment.

The phthalocyanine blue pigment used in the present invention typically has the following formula, and its molecule usually contains 0 to 8 chlorine atoms on average. In addition, M in the formula (1) is a hydrogen atom or one of Cu, Zn, Ni and Fe, and M is generally preferably Cu in view of color tone and cost.

wherein M is a hydrogen atom or one of Cu, Zn, Ni and Fe, and each of X₁ to X₄ is a chlorine atom, provided that the total number of X₁ + X₂ + X₃ + X₄ is 0 to 8.

In the above formula (1), M is preferably Cu in view of color strength, and the total number of X₁ + X₂ + X₃ + X₄ is preferably 2 to 4 in view of heat resistance and color tone.

The indanthrene blue pigment used in the present invention typically has the following formula (2):

A dye can be used to improve clarity and sharpness, but it must be insoluble in water.

The copolymer resin (c) used in the present invention has a high affinity for a pigment and wets the pigment surface well. It is considered that the copolymer resin thereby coats the pigment surface to an appropriate extent and thus prevents the chlorinated water from coming into contact with the pigment in the molded article when it is brought into direct contact with the molded article. The occurrence of bubbles and their flaking are thereby inhibited or prevented.

The above-mentioned copolymer resin preferably has a weight-average molecular weight of 5,000 to 50,000, more preferably 10,000 to 30,000. If the weight-average molecular weight of the copolymer exceeds the above-mentioned upper limit, it may be difficult to produce a so-called masterbatch containing a high concentration of pigment as described later. If the above-mentioned weight-average molecular weight falls below the above-mentioned lower limit, it may have adverse effects on the molded article as a final product in some cases.

The copolymer resin preferably has an acid value of 50 to 800, more preferably 100 to 500. If the acid value of the copolymer resin is less than the above-mentioned lower limit, the copolymer resin does not show sufficient affinity for a pigment and does not form a sufficient coating on the pigment surface, making it difficult to prevent bubbles. If the above-mentioned acid value is more than the upper limit, the copolymer tends to absorb moisture and shows high adhesion to metal, making the extrusion processability of the resin composition more susceptible to deterioration.

The copolymer resin preferably has a melt viscosity of 100 to 2,000 Pa (1,000 to 20,000 poise), more preferably 200 to 900 Pa (2,000 to 9,000 poise). The values of the melt viscosity refer to values obtained by measurement at 160°C with a flow tester. If the melt viscosity is below the above-mentioned lower limit, the dispersion of the pigment is difficult. If the melt viscosity exceeds the above-mentioned upper limit, the coating of the pigment surface with the copolymer resin is rather difficult, and therefore the above melt viscosity is preferably in the range of 1,000 to 20,000.

The above copolymer resin can be obtained, for example, by a method described in JP-A-202234.

For example, the monomer having an α,β-unsaturated double bond is not particularly limited and is typically selected from an α-olefin, a diolefin, an allyl monomer, an N-vinyl monomer, vinyl ether, vinyl sulfide, a methacrylic acid ester monomer and another copolymerizable vinyl monomer or vinylidene monomer. These monomers may be used individually or in combination. Preferably, the monomer having an α,β-unsaturated double bond is a copolymerizable α-olefin.

Specific examples of the α-olefin include ethylene, propylene, butylene, isobutylene, pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 1-docosene, 1-tetracosene, 1-hexacosene, 1-octacosene, 1-triacontene, 1-dotriacontene, 1-tetratriacene, 1-hexatricacontene, 1-octatriacontene, 1-tetracontene and a mixture of at least two of these. The α-olefin can also be selected from commercially available products such as: B. Dialen 128 (C12~18), Dialen 208 (C20~28) and Dialen 39 (at least C30) (supplied by Mitsubishi Chemical Co., Ltd.) and VYBAR 2600 (molecular weight 2,600) and VYBAR 2800 (molecular weight 2,800) (supplied by Toyo Petrolite). From the viewpoint of inhibiting and preventing bubbles on a molded article and their chipping, an α-olefin having 10 to 20 carbon atoms is preferred and an α-olefin having 12 to 14 carbon atoms is particularly preferred.

As the number of carbon atoms in the α-olefin increases, the melt viscosity of the copolymer resin obtained from the α-olefin decreases. When considered in terms of the melt viscosity, the wettability of a pigment increases and the coating effect of the copolymer resin on a pigment is improved.

However, as the number of carbon atoms in the α-olefin increases, the acid value of a copolymer resin obtained from the α-olefin decreases, as do the affinity between the copolymer resin and a pigment and the wettability of a pigment by the copolymer resin. As a result, coating a pigment with the copolymer resin is insufficient, and therefore the inhibiting or preventing effect on the occurrence of blisters or chipping is rather slight. On the other hand, as the number of carbon atoms in the α-olefin decreases, the acid value of a copolymer resin obtained from the α-olefin increases, as do the affinity between the copolymer resin and a pigment and the wettability of a pigment by the copolymer resin. Consequently, it is expected that the occurrence of blisters and chipping on a molded article can be inhibited or prevented by coating a pigment with the copolymer resin. However, as the number of carbon atoms of the α-olefin decreases, the melt viscosity of the copolymer resin increases, and therefore, when considered in terms of melt viscosity, the wettability of a pigment decreases, as does the coating effect of the copolymer resin on a pigment.

When the wettability of a pigment by a copolymer resin, i.e., the coating of a pigment with the copolymer resin, is examined in consideration of both the acid value and the melt viscosity of the copolymer resin, the use of an α-olefin having 10 to 20 carbon atoms is preferred, or the use of an α-olefin having 12 to 14 carbon atoms is particularly preferred to obtain the copolymer resin.

Regarding the monomer having an α,β-unsaturated double bond other than the α-olefin, the diolefin includes butadiene, isoprene, neoprene, chloroprene and a mixture of at least two of these.

The allyl monomer includes allyl acetate, isopropenyl acetate, allyl chloride, isopropenyl chloride, trans-propenyl chloride, cis-propenyl chloride and a mixture of at least two of these.

The N-vinyl monomer includes N-vinylcarbazole, N-vinyl-2-pyrrolidone, N-vinylphthalimide and a mixture of at least two of these.

The vinyl ether includes linear or branched aliphatic alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, isobutyl vinyl ether and hexyl vinyl ether, p-dioxene and a mixture of at least two of these.

The vinyl sulfide includes ethyl vinyl sulfide, phenyl vinyl sulfide and a mixture of these.

The methacrylic acid ester monomer includes acrylic acid esters of linear or branched aliphatic alcohols such as methyl acrylate, ethyl acrylate, Butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate and dodecyl acrylate, methacrylic acid esters corresponding to these acrylic acid esters and a mixture of at least two of these.

The other copolymerizable vinyl monomer or vinylidene monomer includes vinyl ester, vinyl pyridine, vinyl acetate, vinyl propionate, styrene, α-methylstyrene, β-methylstyrene, acrylonitrile, methacrylonitrile, vinylidene chloride and a mixture of at least two of these.

The dibasic acid having an unsaturated double bond or its anhydride includes maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, maleic anhydride, itaconic anhydride and citraconic anhydride. These dibasic acids can be used individually or in combination. Preferably, the dibasic acid having an unsaturated double bond or its anhydride is maleic acid or maleic anhydride. Typically, the copolymer resin is obtained from an α-olefin having 10 to 20 carbon atoms and maleic anhydride.

The copolymer resin of a monomer having an α,β-unsaturated double bond and a dibasic acid having an unsaturated double bond or its anhydride can be produced by any method selected from solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and dispersion polymerization, but the production method is not limited to these. The polymerization initiator used in the above production includes peroxides such as benzoyl peroxide, lauryl peroxide, cumene peroxide, diisopropyl peroxycarbonate, di-tert-butyl peroxide and tert-butyl peroxybenzoate, and azo compounds such as azobisisobutyronitrile and azobis-2,4-dimethylvaleronitrile.

The chlorinated water resistant resin composition may be in the form of pellet (hereinafter sometimes referred to as "colored pellet") used for direct molding or in the form of pellet (hereinafter sometimes referred to as "masterbatch") having a high concentration of pigment and is called a "masterbatch". The masterbatch can be diluted with a polyolefin resin and the resulting mixture molded to obtain a molded article.

Colored pellet preferably contains 100 parts by weight of the polyolefin resin, 0.01 to 10 parts by weight of the pigment and 0.005 to 10 parts by weight of the copolymer resin.

If the amount of pigment is less than 0.01 to 10 parts by weight, only very slight coloring is achieved. If the amount of pigment exceeds 10 parts by weight, the pigment tends to impair the mechanical properties of a molded article. If the amount of a copolymer resin is less than 0.005 parts by weight, almost no effect is achieved on the resistance to chlorinated water. If the amount of copolymer resin exceeds 10 parts by weight, the copolymer resin tends to impair the mechanical properties of a molded article due to poor compatibility with the polyolefin resin.

Furthermore, in order to completely coat the pigment surface with the above-mentioned copolymer resin, the amount of the copolymer resin is preferably at least half the weight of the pigment.

When the resin composition of the present invention is produced as a masterbatch, the resin composition preferably contains 100 parts by weight of the polyolefin resin, 0.1 to 100 parts by weight of the pigment and 0.05 to 100 parts by weight of the copolymer resin.

If the pigment content is less than 0.1 part by weight, it is difficult to obtain a molded article with the desired degree of coloration. If the pigment content exceeds 100 parts by weight, the dispersion of the pigment in the masterbatch is insufficient. If the amount of the copolymer resin is less than 0.05 parts by weight, there is almost no effect on the resistance to chlorinated water. If the amount of the polymer resin exceeds 100 parts by weight, the granulation of the masterbatch is difficult.

Furthermore, in order to completely coat the pigment surface with the above-mentioned copolymer resin, the amount of the copolymer resin is preferably at least half the weight of the pigment.

The masterbatch may be diluted with a polyolefin resin and the mixture may be compression molded to obtain a molded article. The polyolefin resin used for the above dilution is one which is the same as or similar to the polyolefin resin used to prepare the masterbatch.

Similar to the pellet which is directly molded without dilution, the above mixture (diluted masterbatch) for producing a molded article as a final product preferably contains 100 parts by weight of the polyolefin resin, 0.01 to 10 parts by weight of the pigment and 0.005 to 10 parts by weight of the copolymer resin.

When the masterbatch and the colored pellet are compared, their manufacturing steps are not very different, although the masterbatch is slightly more expensive since it contains a high concentration of pigment. However, the masterbatch can be diluted with 0.5 to 200 parts by weight of an inexpensive polyolefin resin based on the masterbatch to obtain a molded article. When the molded articles are compared as final products, the molded article is produced from the masterbatch diluted with a polyolefin resin, since the molded article produced from a masterbatch diluted with a polyolefin resin is less expensive.

The colorant (colored) resin composition having resistance to chlorinated water can be molded into articles in the form of a film, sheet, plate, container, pipe or fiber. In addition, the colorant (colored) resin composition has excellent resistance to chlorinated water and can therefore be preferably used for producing a water supply pipe. The term "pipe", as used in the present invention comprises the pipe itself and a part used for connecting pipes (connecting part).

The colorant (colored) resin composition used in the present invention may contain, as required, a metallic soap, a dispersant such as medium or low molecular weight polyethylene, an antioxidant and an ultraviolet absorber in amounts not detrimental to the resistance of the resin composition to chlorinated water.

Examples

The present invention will be explained in more detail below with reference to Examples. First, the production process for the copolymer resin of the monomer having an α,β-unsaturated double bond and the dibasic acid having an unsaturated double bond or its anhydride will be explained below. In the following Examples, "%" means "percent by weight" and "part" means "part by weight".

Manufacturing example 1

A flask was charged with 650 g of an α-olefin having 12 to 14 carbon atoms, 4.4 g of di-tert-butyl peroxide and 14 g of toluene, and the atmosphere in the flask was replaced with nitrogen. While stirring the mixture at 150°C, maleic anhydride was added at 2 minute intervals, 11.7 g each to make the total amount 350 g, and di-tert-butyl peroxide was added at 20 minute intervals, 1.1 g each to make the total amount 4.4 g. After this addition, 1 g of di-tert-butyl peroxide was additionally added and the mixture was kept at 160°C to react the mixture for an additional 6 hours. After completion of the reaction, the hot-discharged contents were cooled until solidified, thereby obtaining a copolymer resin having a weight-average molecular weight of 17,000, an acid value of 400 and a melt viscosity of 300 Pa (3,000 poise) (measured at 160ºC with a flow tester).

Manufacturing example 2

A flask was charged with 50 g of an α-olefin having 10 carbon atoms, 930 g of an α-olefin having a number average molecular weight of 2,600, 0.44 g of di-tert-butyl peroxide and 1.4 g of toluene, and the atmosphere in the flask was replaced with nitrogen. While stirring the mixture at 150°C, maleic anhydride was added at 1.17 g each at 2 minute intervals to make the total 35 g, and di-tert-butyl peroxide was added at 0.11 g each at 20 minute intervals to make the total 0.44 g. After this addition, an additional 0.1 g of di-tert-butyl peroxide was added and the mixture was kept at 160°C to react the mixture for an additional 6 hours. After completion of the reaction, the hot-discharged contents were cooled until solidified, thereby obtaining a copolymer resin having a weight-average molecular weight of 18,000, an acid value of 100 and a melt viscosity of 400 Pa (4,000 poise) (measured at 160ºC with a flow tester).

Manufacturing example 3

A flask was charged with 595 g of an α-olefin having 10 carbon atoms, 4.0 g of di-tert-butyl peroxide and 14 g of toluene, and the atmosphere in the flask was replaced with nitrogen. While stirring the mixture at 150°C, maleic anhydride was added at 13.5 g each at 2 minute intervals to make the total 405 g, and di-tert-butyl peroxide was added at 1.0 g each at 20 minute intervals to make the total 4.0 g. After this addition, an additional 1.0 g of di-tert-butyl peroxide was added and the mixture was kept at 160°C to react the mixture for an additional 6 hours. After completion of the reaction, the hot-discharged contents were cooled until solidified, thereby obtaining a copolymer resin having a weight-average molecular weight of 22,000, an acid value of 460 and a melt viscosity of 1,800 Pa (18,000 poise) (measured at 160ºC with a flow tester).

Manufacturing example 4

A flask was charged with 1,276 g of an α-olefin having 20 to 28 carbon atoms, 3.6 g of di-tert-butyl peroxide and 14 g of toluene, and the atmosphere in the flask was replaced with nitrogen. While stirring the mixture at 150°C, maleic anhydride was added at 2 minute intervals, 13.7 g each to make the total amount 412 g, and di-tert-butyl peroxide was added at 20 minute intervals, 0.9 g each to make the total amount 1.8 g. After this addition, 1 g of di-tert-butyl peroxide was additionally added and the mixture was kept at 160°C to react the mixture for an additional 6 hours. After completion of the reaction, the hot-discharged contents were cooled until solidified, thereby obtaining a copolymer resin having a weight-average molecular weight of 5,500, an acid value of 270 and a melt viscosity of 150 Pa (1,500 poise) (measured at 160ºC with a flow tester).

example 1

50 parts of the resin obtained in Preparation Example 1 and 50 parts of phthalocyanine blue (Pigment Blue 15:3) were kneaded with a kneader to obtain a masterbatch intermediate. Then, 100 parts of a high-density polyethylene (MFR = 0.062 g/10 min. (190°C, 2.16 kg), density 0.952 g/cm3) and 3.2 g of the above masterbatch intermediate were mixed with a Henschel mixer, and the mixture was extruded with a single-screw extruder at 220°C to obtain strands. The strands were cooled and pelletized to obtain a masterbatch. Then, 100 parts of a high-density polyethylene and 5 parts of the masterbatch were mixed, and the mixture was injection-molded with an injection molding machine to prepare a test plate. The test panel was subjected to a chlorinated water resistance test under the following conditions in accordance with JIS K6762 to determine the occurrence of bubbles. The results are shown in Table 1.

* Test conditions

Chlorine concentration: 2,000 ± 100 ppm

Temperature: 60ºC

Immersion time: 168 hours

*Rating scale

1 = At least 10 point-shaped protrusions or bubbles of small diameter of at least 0.4 mm were found in an area of 1 cm² on the plate surface.

2 = Four to nine point-like protrusions or bubbles of small diameter of at least 0.4 mm were found in an area of 1 cm² on the plate surface.

3 = Three or two point-shaped protrusions or bubbles of small diameter of at least 0.4 mm were observed in an area of 1 cm² on the plate surface.

4 = One or no point-like protrusion or bubble of small diameter of at least 0.4 mm was observed in an area of 1 cm² on the plate surface.

Example 2

A masterbatch was obtained in the same manner as in Example 1 except that 50 parts of the resin obtained in Preparation Example 1 was replaced with 25 parts of a low molecular weight polyethylene and 25 parts of the resin obtained in Preparation Example 1. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 3

A masterbatch was obtained in the same manner as in Example 2 except that the amount of the masterbatch intermediate was changed from 3.2 parts to 1.6 parts. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for durability against chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 4

A masterbatch was obtained in the same manner as in Example 2 except that the amount of the masterbatch intermediate was changed from 3.2 parts to 0.5 parts. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 5

A masterbatch was obtained in the same manner as in Example 2 except that the amount of the masterbatch intermediate was changed from 3.2 parts to 10 parts. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 6

A masterbatch was obtained in the same manner as in Example 1 except that 50 parts of the resin obtained in Preparation Example 1 was replaced with 50 parts of the resin obtained in Preparation Example 2. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 7

A masterbatch was obtained in the same manner as in Example 1 except that the amount of the masterbatch intermediate was changed from 3.2 parts to 20 parts. 10 parts of the masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 8

A masterbatch was obtained in the same manner as in Example 2 except that the amount of the masterbatch intermediate was changed from 3.2 parts to 0.8 parts. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 9

A masterbatch was obtained in the same manner as in Example 1 except that the phthalocyanine blue was replaced with indanthrene blue (Pigment Blue 60). The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 10

100 parts of a high density polyethylene (MFR = 0.062 g/10 min. (190ºC, 2.16 kg), density 0.952 g/cm³), 1.6 parts of the resin obtained in Preparation Example 1 and 1.6 parts of phthalocyanine blue (Pigment Blue 15:3) were mixed and the mixture was kneaded and extruded with a single-screw extruder at 220ºC to obtain a colored Then, the colored pellet was fed into an injection molding machine to obtain a test plate, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 11

Colored pellet was obtained in the same manner as in Example 10 except that the phthalocyanine blue was replaced with indanthrene blue (Pigment Blue 60). Then, the colored pellet was fed into an injection molding machine to obtain a test plate, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 12

A masterbatch was prepared in the same manner as in Example 1 except that 50 parts of the resin obtained in Preparation Example 1 was replaced with 50 parts of the resin obtained in Preparation Example 3. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Example 13

A masterbatch was prepared in the same manner as in Example 1 except that 50 parts of the resin obtained in Preparation Example 1 was replaced with 50 parts of the resin obtained in Preparation Example 4. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1.

Comparison example 1

A masterbatch was prepared in the same manner as in Example 1 except that 50 parts of the resin obtained in Preparation Example 1 was replaced with 50 parts of a low molecular weight polyethylene. The masterbatch was used to prepare a test plate in the same manner as in Example 1, and the test plate was tested for resistance to chlorinated water in the same manner as in Example 1 to determine the occurrence of bubbles. The result is shown in Table 1. Table 1

Bsp. = example, Vbsp. = comparative example

The above results show that the present invention uses a colorant (colored) resin composition having resistance to chlorinated water, from which molded articles having excellent resistance to chlorinated water can be obtained.

Claims (11)

1. Use of a resin composition comprising: (a) a polyolefin resin; (b) a pigment; and (c) a copolymer resin preparable from a monomer having an α,β-unsaturated double bond and a dibasic acid having an unsaturated double bond or an anhydride thereof, when transporting water containing chlorine. 2. Use according to claim 1, wherein the resin composition contains 100 parts by weight of the polyolefin resin, 0.01 to 10 parts by weight of the pigment, and 0.005 to 10 parts by weight of the copolymer resin. 3. Use according to claim 1, wherein the resin composition contains 100 parts by weight of the polyolefin resin, 0.1 to 100 parts by weight of the pigment, and 0.05 to 100 parts by weight of the copolymer resin. 4. Use according to any one of the preceding claims, wherein the monomer having an α,β-unsaturated double bond is a copolymerizable α-olefin. 5. Use according to any one of the preceding claims, wherein the dibasic acid having an unsaturated double bond or the anhydride thereof is maleic acid or maleic anhydride. 6. Use according to claim 5, wherein the copolymer resin is preparable from an α-olefin having 10 to 20 carbon atoms and maleic anhydride. 7. Use according to any one of the preceding claims, wherein the pigment is a blue pigment. 8. Use according to claim 7, wherein the blue pigment is a phthalocyanine blue pigment and/or an indanthrene blue pigment. 9. Use according to claim 8, wherein the phthalocyanine blue pigment is a copper phthalocyanine blue pigment. 10. A water supply pipe made from a resin composition as defined in any of the preceding claims. 11. Water supply pipe according to claim 10, which is a drinking water pipe.